The principal objectives of this proposal are to study effects of cytomegalovirus (CMV) infection on embryonic development and to examine the modes by which infection produces maldevelopment. Evidence from studies of human CMV indicates that infection during early pregnancy can result in teratogenic effects in the fetus and mild to severe fetal damage leading to death or later manifested in any of a number of physical and behavioral problems in children. Aims are to (1) follow the course of maldevelopment in mouse CMV (MCMV) infected mouse embryos, (2) study the manner of MCMV gene expression during early embryonic differentiation in vitro, and (3) examine a possible means of MCMV transmission by sperm into the egg at fertilization and the consequences of this on fetal development. The first of these aims will be accomplished by setting up situations in the female mouse designed to result in congenital infections. These will include surgical intrauterine inoculation of free virus and reactivation of latent maternal infection at early gestation. Preliminary results support both of these means of effecting congenital infections in mice. Resulting maldevelopment will be followed by scanning electron microscope in early stage embryos and by conventional biopathologic studies in later stage fetuses. Immunologic and DNA localization studies will also be performed. The second aim will involve in vitro studies of early stage mouse embryos. Isolation of the inner cell mass from pre-infected blastocyst stage embryos and subsequent culture will allow study of gene expression during critical points of early differentiation into primary germ layers. Electron microscopy will be used to detect virus in developing tissue, immunofluorescence for the detection of MCMV specific antigens and in situ nucleic acid cytohybridization for precise localization of MCMV DNA. Lastly, the possibility that CMV infected sperm may serve as a vector in the transmission of viral genome into the ovum will be examined using both in vivo and in vitro fertilization techniques and by artificial microinjection of MCMV or MCMV DNA directly into the ovum. Eggs thus treated will be implanted into surrogate mice and development will be monitored. Attempts will be made to demonstrate the presence of MCMV genome in the eggs using in situ nucleic acid cytohybridization. These studies should provide valuable information concerning CMV mediated congenital maldevelopment as the mouse model has been shown to have relevant applications in other areas of human CMV investigation.